Light is an important abiotic factor that determines the distribution and abundance of plants. Some plants are adapted to grow in areas of low light intensity. They are known as shade plants. Some students investigated the abundance of dog’s mercury, Mercurialis perennis, under forest trees in eight different locations. At each location, they used ten randomly positioned quadrats to measure the percentage cover of this shade plant.

a. Draw a scatter graph to see if there is a correlation between light intensity beneath the canopy and abundance of M. perennis.

b. State a null hypothesis for this investigation.

c. Use the data in the table to calculate the Spearman rank correlation, r_s. Show all your working.

d. What can you conclude from your calculation? You will need to consult Table P2.8 on page 504 to help you answer this question.

Table P2.8

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Light intensity at ground level/ percentage of full sun Mean percentage cover of M. perennis Location A 90 10 B 50 65 30 90 D 20 80 E 80 34 88 20 G. 93 10 100